Young Horses Use Extra Minerals for Bone Growth When Beginning Training

David W. Freeman, OSU Extension Equine Specialist

A recently published research report adds to the ever-growing evidence that exercise causes young, growing horses to have large needs for calcium and perhaps phosphorus and magnesium. The report from TAMU stresses that the most critical time of need is the first couple of months that exercise is started, especially 30 to 60 day post initiation. Apparently, bone turnover is increased as a result of beginning an exercise program with young horses (2 yr olds). The report suggests that increasing levels above currently recognized recommendations may increase bone growth, both by increasing the lay down of new bone, and decreasing the amount broken down as part of normal bone growth.

Overall, this report suggested calcium, phosphorus and magnesium levels that optimized bone deposition in young horses (long yearling Quarter Horses) starting an exercise program should be around 55, 21 and 14 grams per day. This includes balancing all sources including hay. So young horses consuming a grain-hay diet (hay representative of a high quality grass hay), at ratios of 60:40 grain to hay, then the grain mix should contain about 0.4% calcium, 0.2% phosphorus and 0.1% magnesium. Those trainers feeding comparatively less grain and more hay may need to increase the percent of these minerals even more.

Those feeding grain mixes commercially formulated for exercising and growing horses will likely meet this heightened level indicated in the report without additional supplementation of calcium, phosphorus or magnesium. Feed manufacturers routinely add these minerals to the higher levels in mixes balanced for exercising and young horses. You can check the amount of calcium and phosphorus on the feed tag. If it appears that there are insufficient levels, you can top dress a supplement.

Those feeding grains, such as corn-oat mixes without supplemental minerals, will have to add minerals to the grain mix to raise the lower than desired levels. Non supplemented grain mixes are especially low in calcium as compared to desirable levels reported in this study. There is a multitude of supplements that have calcium, phosphorus and magnesium as part of a supplemental mix. It isn't possible to give a recommendation of how much supplement to add as supplements vary greatly in concentration of these minerals.

Most often, the mineral supplement will provide adequate levels of these minerals when you top dress them to the grain at levels recommended on the product label. Just make sure there is more calcium than phosphorus in the supplement, as calcium will be the most if not only, one of the three that isn't at adequate levels when feeding nonformulated grain mixes. One that has at least two or three times the calcium concentration as phosphorus may be best to meet the high levels of calcium needed as compared to the amounts naturally found in grains.